The invention concerns balloon brachytherapy.
Balloon brachytherapy has been known since at least the 1950s, and involves placing a source of radiation within the body, generally near a tumor or within an excision site following removal of a tumor. The purpose or objective is to irradiate the tumor or the margins around the tumor excision cavity. The usual further objective is to provide dose levels of radiation to a target tissue volume surrounding the excision cavity which attain a therapeutic minimum, but below a level capable of producing significant normal-cell tissue necrosis. To accomplish this, a balloon applicator is employed into which the source of radiation is positioned.
Several improvements in applicator design are desirable. In anticipation of radiation therapy to follow complete or partial tumor excision, applicators can be placed within the excision cavity intraoperatively, i.e., during the surgical procedure and before the resection incision is closed. They may also be placed during a separate procedure at a later date when it has been decided to proceed with radiation therapy. Access to the excision cavity for radiation therapy may be through the original incision, or through a different incision purposely created for the applicator. A separate access site might be preferred if the anticipated dose distribution from the brachytherapy protocol, given the location of the excision cavity and proximity to sensitive tissue structures, might place those tissues at risk. When placed intraoperatively, the incision is closed around a sheath, which extends through and outside the skin of the patient. The applicator balloon is usually inflated when the incision is closed, and remains in place until radiation treatment is abandoned or the protocol completed, at which time the balloon is deflated and the applicator surgically removed.
Current or prior art balloon applicators include those described in J. H. Muller, Radiotherapy of Bladder Cancer by Means of Rubber Balloons Filled In Situ with Solutions of a Radioactive Isotope (Co60), Cancer, September-October, 1955, pp 1035-1043; The Clinical Use of Radioisotopes, B. V. A Low-Beer, Charles C. Thomas Publ., 1950; A New Technique of Brachytherapy for Malignant Gliomas with Caesium 137: A New Method Utilizing a New Afterloading System, R. D. Ashpole, et al, Clinical Oncology, vol. 2, 333-337, (1990); and U.S. Pat. No. 5,566,221. Radiation sources used for brachytherapy include small x-ray tubes as disclosed in U.S. Pat. Nos. 5,566,221, 6,319,188, and 6,987,835. Solid high-dose radiation isotope sources may be used, for example those sold by Varian Medical Systems, Inc., Palo Alto, Calif., and fluid isotope sources, for example a solution or slurry of radionuclides such as I-125 or Au-198. X-ray tubes offer both patient and therapist advantages including substantially reduced amounts of radiation and control of the radiation source. Radioisotope sources must be used inside bunkers lined with lead or other absorbers, with the patient being isolated in the bunker. Use of x-ray tubes is not subject to these restrictions. Unlike an x-ray tube, radioisotopes cannot be turned on and off, but rather emit radiation continuously. Those skilled in the art will appreciate that there are additional substantial differences between x-ray tube brachytherapy and radionuclide brachytherapy.
Radiation treatment often follows days after surgery, but preferably it follows weeks after surgery [See Breast Cancer Research and Treatment, J. J. Jobson, et al (2006) 99:289294]and such protracted exposure of the surgical wound at the entry of the applicator sheath through the skin prior to commencing radiotherapy provides a substantial risk of infection that can compromise the resection cavity, and cause additional serious complications for the patient. Also, there can be significant discomfort if the applicator is placed intraoperatively and remains indwelling for an extended period and is perhaps inflated later prior to radiotherapy, or is placed and inflated later in a subsequent procedure, disturbing anatomy which is still sensitive from the resection. It would be beneficial to have an applicator and method which would minimize or eliminate this discomfort and infection risk, but otherwise offer the same or improved functionality and convenience as current applicators. Copending application Ser. No. 10/464,140, filed Jun. 18, 2003, discloses methods of intraoperative brachytherapy using electronic x-ray tubes, and the disclosure of that application is incorporated by reference herein. Copending application Ser. No. 11/811,069 discloses an everting gynecological discloses an everting gynecological applicator, and the disclosure of that applicator is also incorporated by reference herein.